This invention relates to underwater petroleum production, and more particularly to apparatus for conducting petroleum and other fluids from a subsea base to a storage or loading facility at the water surface. The invention especially pertains to riser pipe systems between a location on the ocean floor and a terminal on a floating production platform.
In the production of crude oil and other petroleum fluids from an underwater well, a floating platform containing equipment for storing the produced fluids or for transferring these fluids to a marine tanker or other transport vessel is often used at the water surface. Although these floating platforms are securely anchored in position over the underwater well, the surface effects of wind, waves, and water currents cause some movement of the platform, and in areas such as the North Sea where these surface conditions frequently are very severe the extent of platform movement can be quite significant.
Because of this problem, it has been difficult to establish and maintain an adequate conduit system to conduct the petroleum from the underwater wellhead to the platform, and especially to provide such a conduit, or riser system as it is termed in the industry, that will withstand the movements of the platform during severe weather conditions.
Another problem particularly related to the deeper offshore areas of petroleum production is that the use of divers to assist in the installation and maintenance of underwater well equipment is very expensive, and the efficiency of diver activity at great depths is very low.